Influence of sonication on anticorrosion properties of a sulfursilane film dopped with Ce (IV) on galvannealed steel

Currently, galvannealed carbon steel has been submitted to phosphatizing and/or chromatizing as surface pre-treatments; however, for economic and environmental issues, the viability of using silanes as an alternative pre-treatment has been studied. The aim of this work is to study the effect of sonication of the solvent solution (50/50%, m/m water/ethanol) with 50 ppm of Ce (IV) ions on the corrosion behavior of bis-1.2-triethoxysilylpropyl]tetrasulfide (BTESPT) silane film deposited on galvannealed steel. The sonication influence on reactions has been studied and seems to promote the formation of small molecules starting from large ones, the change of the local pH and temperature, beyond the change of the solution viscosity. The corrosion resistance of the steel coated samples was evaluated by electrochemical impedance spectroscopy (EIS), linear polarization resistance (R_p) and potentiodynamic polarization curves. The molecular vibrational and chemical properties of the films were obtained by infrared (IR) and micro Raman spectroscopies. The physical characterization of sonicated solutions was performed by measuring their kinematic viscosity. The images from scanning electron (SEM) microscope were obtained to characterize the aspect and morphology of the film. The results showed that the sonication led to obtaining more homogeneous, compact and corrosion resistant silane films.